Viscous products, such as comestibles, paints, toothpastes, lotions, cosmetics, or cleaning products to suggest but a few are often stored and dispensed from a container, jar, tube, or other packaging with a relatively narrow dispensing opening or mouth. Due to the viscous nature of these products, a residual amount may be left in the bottom or corners of the container during normal use. In many cases, due to the particular geometry of the container, the consumer is unable to retrieve such residual product even with the use of an extra utensil to scrape the inside of the container. The container may have a small dispensing nozzle that is not sized for receipt of a utensil or, even if a utensil can be inserted through the mouth, the container may have regions that cannot be accessed by the utensil. This unused, residual product often remains in the container and is disposed of along with the container.
The container can be redesigned to improve product evacuation, but such redesigns can be costly and may not result in a significant decrease in the amount of residual product left in the container after normal use. For example, product release from a container can, in some cases, be improved by modifying the container shape or geometry to have shoulder portions that minimize the amount of residual product that remains in such areas. However, as indicated above, redesigning a container shape is costly because new molds are typically required.
Other attempts to improve product release involve modifying the inner surface of the containers. The entire container inner surface may be corona or plasma treated to modify the surface energy/wetting tension ability of the packaging material or a release coating may be applied to the entire inner surface of the container to provide a surface that the material may more easily release from. For example, U.S. Pat. No. 6,247,603 B1 discloses coating either soybean oil or olive oil to the entire inner surfaces of a container. Other references, such as U.S. Pat. Nos. 2,832,701; 2,504,482; and 6,599,594 also suggest applying various coatings to the entire inner surfaces of containers. These methods have shortcomings that may detrimentally affect the visual appearance of the product and/or potentially degrade product quality within the container during shipment. The shortcomings may be especially apparent when the viscous material is an emulsion or aerated product or when the container is transparent so that the product can be viewed by the consumer.
It has been discovered that a surface treatment or coating applied to the entire inner surface of a container may affect the stability of some viscous materials. For example, when the viscous material is an emulsion or aerated material, the surface treatment or release coating applied to the entire inner surface of the container can result in oiling-off or overrun collapse of the product. It is believed that such instability results from the viscous material not being able to stick to the container walls adjacent a product/container interface at the top surface of the material because of the coating or surface treatment. As a result, during shipment of the container, the material adjacent this interface moves or slides about the container wall. The resulting mechanical energy from this product motion may cause the emulsion to separate, forming a layer of oil on the surface of the material, or may cause a portion of the overrun to collapse, resulting in a decrease in product volume. Such instability is most apparent after vibration of the container encountered during product shipping.
Existing coatings also have other shortcomings. For example, the '603 patent discloses a coating of either soybean oil or olive oil. These oils have undesired physical characteristics that render them less desirable for use as a release coating—especially when the coating is applied to a clear or transparent container. These oils typically have a yellowish and/or greenish tint. Therefore, when coated on the inner surfaces of a transparent container, the soybean or olive oil coatings will potentially alter the physical appearance of the product within the container. For example, if the product is a generally white mayonnaise-type material, toothpaste, or lotion, then a yellowish or greenish oil coating on the inner surfaces of a transparent container may impart a color change to the white product. Such a change in appearance may render the product undesirable to a consumer because they may not associate such off-colors with the product in the container. Soybean and olive oil also have a viscosity profile that substantially changes between room and refrigeration temperatures, such that evacuation of viscous materials that have been stored in refrigerators may be substantially reduced.
Coatings that use soybean oil or olive oil are also subject to oxidation. These oils comprise substantial amounts of unsaturated fatty acids that tend to be unstable and prone to oxidation. Soybean and olive oil, for example, may contain greater than 70 percent unsaturated fatty acids. Once the container is opened, these soybean and olive oil coatings may become rancid over time if not properly stored due to oxidation. Such chemical changes to the coating may also create the perception to a consumer that the viscous material in the container is no longer usable.
A container having the entire inner surfaces coated may also be perceived by a consumer as being less desirable because such a container would appear to have less product than a traditional, uncoated container—even if filled with the same amount or volume of product. With the traditional, uncoated container holding a viscous material, the container generally appears completely full even though the product volume may be slightly less than a full container. With the uncoated container, the viscous material is allowed to generally adhere to the container walls and, therefore, the container appears to a consumer to be completely full without any unsightly bubbles or void areas of the product being visible. On the other hand, with the coating techniques of the prior art, a container completely coated or surface treated on its inner walls to form a release surface may appear less full than a corresponding uncoated container or have unwanted void areas or bubbles because the viscous material is no longer capable of adhering to the container inner surfaces and slides off from such surfaces. As a result, visible empty areas may be present in various portions of the container depending on the container's orientation. Such a container may be less desirable to the consumer.
Accordingly, there is a desire for a container that is effective to facilitate improved product release that also generally maintains product stability.